The present invention relates to light emitting diodes (LEDs) and more particularly to LEDs having color and intensity correction.
Light emitting diodes (LEDs) appear in many different applications, such as illuminating controls, automotive signals, and displays. Many applications use multiple LEDs in a single device, but color and light intensity tolerance ranges for LEDs can be large and result in a non-uniform appearance, both within a single device and across multiple devices. To accommodate these wide color and intensity variations, LED manufacturers often sort each LED into a particular color and/or intensity xe2x80x9cbinxe2x80x9d, thereby minimizing variances within a selected LED group. For example, if a manufacturer sorts LEDs by intensity, a single bin may contain parts that have a luminous intensity range of 100 to 200 millicandela.
If a high-volume end user requires LEDs having the specific characteristics exhibited in one intensity and/or color bin, the LED manufacturer must produce a sufficient quantity of LEDs for that bin as a percentage of all of the LED dies produced for a target color. Tight bin tolerances cause the LEDs contained in that bin to constitute a small portion of the total LED yield. It may be necessary for the user to accept multiple adjacent bins to fulfill quantity requirements. This process tends to be expensive and impractical for large production quantities because shortages may occur if the bins meeting production criteria constitute a relatively small fraction of the LED manufacturer""s overall production.
The problem is further complicated when an application requires color mixing of LEDs because the large tolerances for individual LEDs are magnified during color mixing, resulting in substantial, noticeable system level color variations.
There is a need for a method and system that reduces color and intensity variations in LEDs.
Accordingly, the present invention is directed to a light emitting diode (LED), comprising an LED die that emits light in an optical path and a filter disposed in the optical path, wherein the filter has a filter pattern that changes at least one of the color and the intensity of the emitted light, wherein the filter pattern is generated based on a shift value corresponding to a deviation between at least one of the color and intensity of the emitted light from a reference.
The invention is also directed to an apparatus having at least one light emitting diode (LED), comprising at least one LED die that emits light in an optical path, at least one LED lens in the optical path of said at least one LED die, and at least one filter disposed on said at least one LED lens, wherein the filter is a printed ink pattern that changes at least one of the color and the intensity of the emitted light, wherein the filter pattern is generated based on a shift value corresponding to a deviation between at least one of the color and intensity of the emitted light from a reference.
The invention is further directed to a method for correcting at least one of a color and intensity of emitted light along an optical path from an LED die, comprising the steps of measuring at least one of the color and intensity of the emitted light, comparing said at least one of the color and intensity of the emitted light with a reference to obtain a shift value, and placing a filter in the optical path, wherein the filter has a filter pattern that changes at least one of the color and the intensity of the emitted light based on the shift value.